Conventional magnetic resonance (MR) images are obtained from the 1H nuclei in water and fat. The resolution of such images is usually 1 mm × 1 mm in plane with a slice thickness of either 3 or 5 mm. Different tissues can be distinguished by the difference in the density and macromolecular environment of their mobile protons. The intensity of tissue signals is influenced by three main parameters: proton density (PD), T1 relaxation time and T2 relaxation time. T1 and T2 relaxation times define the rate at which the nuclear MR signals decay after the radiofrequency excitation pulse ceases (T1: longitudinal relaxation i.e. parallel to the magnetic field; T2: transverse relaxation, i.e. perpendicular to the magnetic field). PD and T2-weighted spin echo sequences (or their more rapidly acquired modification, the fast spin echo) are the most widely used for diagnostic studies in multiple sclerosis (MS). They have high specificity for tissue abnormality and the relation between MRI and tissue abnormalities in MS has been studied using post-mortem material [1–3].
KeywordsExpand Disability Status Scale Progressive Multiple Sclerosis Expand Disability Status Scale Score Lesion Load Primary Progressive Multiple Sclerosis
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